The coolant used for cooling an internal combustion engine is a liquid which is subject to acquiring suspended air bubbles (i.e., aerated coolant) in the course of its flow through various coolant passages within the engine. Since the presence of air bubbles in the coolant is undesirable, as for example it reduces coolant volume and surface contact area for heat transfer and can impede coolant flow, some mechanism is usually provided to promote removal of the air bubbles from the coolant.
FIGS. 1 and 2 depict an exemplification of a passive de-aeration system 10 used in the prior art. An internal combustion engine 12 has a block 14, a head 16, and an associated coolant system 18. The coolant system 18 includes a liquid coolant which flows through a plurality of coolant passages 42 within the block and the head, and connects via coolant lines 44 to a heater core 20, a radiator 22, a thermostat 24 and a pump 26, all components being well known in the automotive arts.
The prior art passive de-aeration system 10 is also a component of the coolant system 18 for removing air bubbles from the coolant. A coolant fill tube 30 is vertically oriented and has at its top end 30a a pressure cap 32 which has a twist fit connection to the fill tube. The fill tube 30 is about 150 mm in length L between its top end 30a and bottom end 30b, and is about 40 mm in diameter D. The pressure cap 32 is of a type well known in the automotive arts, wherein for situations of below a predetermined coolant pressure (for example, around 70 kPa), air escapes through a vent passage 34 in the pressure cap to an overflow nipple 36; however, if pressure exceeds the predetermined pressure, then the internal sealing of the pressure cap is released with respect to an annular cap seal lip 30c of the fill tube and coolant 40 can then travel out via the overflow nipple. The bottom end 30b of the fill tube 30 opens to a highest elevation coolant passage 42a of the plurality of coolant passages 42, as for example at the head 16, such that the fill tube rises vertically at the highest point in the coolant system 18.
In operation, coolant 40 flows (see arrows F) in a coolant passage 42, wherein air bubbles 38 travel in suspension in the coolant and pass below the fill tube 30. Passively, under urge of buoyancy some air bubbles will drift upwardly into the stagnant pool 40a of the coolant 40 situated within the fill tube 30. The air bubbles 38 find the surface and merge with the air A thereabove, whereupon the increased pressure caused thereby is released by air passing-out through the vent passage 34.
While the aforedescribed coolant system and its associated de-aeration system provide removal of air bubbles within the coolant, the passive nature of the de-aeration involving a stagnant coolant pool and the passivity of buoyancy, air bubble movement from the coolant passage and into the prior art passive de-aeration system is at a very slow pace, such that the air bubbles must, on average, make very many circuits of the coolant path before successfully finding the fill tube.
Accordingly, what remains needed in the prior art is an active de-aeration system for an automotive coolant system, wherein coolant is actively freed of suspended air.